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1.
Artigo em Inglês | MEDLINE | ID: mdl-32298024

RESUMO

Graphite shows great potential as an anode material for rechargeable metal-ion batteries because of its high abundance and low cost. However, the electrochemical performance of graphite anode materials for rechargeable potassium-ion batteries needs to be further improved. Reported herein is a natural graphite with superior rate performance and cycling stability obtained through a unique K+ -solvent co-intercalation mechanism in a 1 m KCF3 SO3 diethylene glycol dimethyl ether electrolyte. The co-intercalation mechanism was demonstrated by ex situ Fourier transform infrared spectroscopy and in situ X-ray diffraction. Moreover, the structure of the [K-solvent]+ complexes intercalated with the graphite and the conditions for reversible K+ -solvent co-intercalation into graphite are proposed based on the experimental results and first-principles calculations. This work provides important insights into the design of natural graphite for high-performance rechargeable potassium-ion batteries.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32297392

RESUMO

Although organic ionic crystals represent an attractive class of active materials for rechargeable batteries owing to their high capacity and low solubility in electrolytes, they generally suffer from limited electronic conductivity and moderate voltage. Furthermore, the charge storage mechanism and structural evolution during the redox processes are still not clearly understood. Here we describe ethyl viologen iodide (EVI2 ) and ethyl viologen diperchlorate (EV(ClO4 )2 ) as cathode materials of lithium batteries which crystallize in a monoclinic system with alternating organic EV2+ layers and inorganic I- /ClO4 - layers. The EVI2 electrode exhibits a high initial discharge plateau of 3.7 V (vs. Li+ /Li) because of its anion storage ability. When I- is replaced by ClO4 - , the obtained EV(ClO4 )2 electrode displays excellent rate performance with a theoretical capacity of 78 % even at 5 C owing to the good electron conductivity of ClO4 - layers. EVI2 and EV(ClO4 )2 also show excellent cycling stability (capacity retention >96 % after 200 cycles).

3.
ChemSusChem ; 2020 Feb 05.
Artigo em Inglês | MEDLINE | ID: mdl-32022410

RESUMO

In contrast to traditional rechargeable rock-chair metal-ion batteries, dual-ion batteries (DIBs) involve redox reactions with anions rather than cations in p-type cathodes. In principle, regulating the electrochemical performance of the DIB by different anion species is highly feasible. Herein, the anion effect on the electrochemical performance of a DIB, the aqueous Zn- organic radical battery (Zn-ORB), consisting of a poly(2,2,6,6tetramethylpiperidinyloxy-4-yl vinyl ether) cathode and a Zn anode, was investigated by DFT calculations. SO4 2- , CF3 SO3 - , and ClO4 - with different molecular electrostatic potential values were selected as anion models. DFT calculations revealed that a stronger electrostatic interaction of the anion with the organic radical resulted in a higher operating voltage of the Zn-ORB, which was consistent with experimental results. These results bring new insight into the redox chemistry of p-type organic radicals with anions and will promote the development of high-power aqueous Zn-ORBs as well as inspire more investigations into the anion effect towards novel battery designs.

4.
Nat Commun ; 11(1): 178, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31924753

RESUMO

Covalent organic frameworks with designable periodic skeletons and ordered nanopores have attracted increasing attention as promising cathode materials for rechargeable batteries. However, the reported cathodes are plagued by limited capacity and unsatisfying rate performance. Here we report a honeycomb-like nitrogen-rich covalent organic framework with multiple carbonyls. The sodium storage ability of pyrazines and carbonyls and the up-to twelve sodium-ion redox chemistry mechanism for each repetitive unit have been demonstrated by in/ex-situ Fourier transform infrared spectra and density functional theory calculations. The insoluble electrode exhibits a remarkably high specific capacity of 452.0 mAh g-1, excellent cycling stability (~96% capacity retention after 1000 cycles) and high rate performance (134.3 mAh g-1 at 10.0 A g-1). Furthermore, a pouch-type battery is assembled, displaying the gravimetric and volumetric energy density of 101.1 Wh kg-1cell and 78.5 Wh L-1cell, respectively, indicating potentially practical applications of conjugated polymers in rechargeable batteries.

5.
ChemSusChem ; 2020 Jan 22.
Artigo em Inglês | MEDLINE | ID: mdl-31968154

RESUMO

The n-type phenazine (PZ) derivatives represent an emerging class of cathode materials in lithium batteries for low-cost and sustainable energy storage. However, their low redox potential (<2 V) and high solubility hinder their application to battery systems. To explore and solve such problems in lithium batteries, we investigate the redox characteristics of 13 n-type PZ derivatives and their dissolution behavior in seven organic electrolytes systematically by using DFT calculations. Two decisive factors are observed to tune the redox potentials for these molecules: the first is the electron density around the N active sites and the second is the chelation on lithium by both the active N and the substituent group. Specific approaches that include the reduction of aromatic rings and the introduction of functional groups at ß sites in n-type PZ derivatives can improve the redox potential to approximately 3 V. In addition, we develop a new index denoted as Ediff to investigate the solubility of n-type PZ derivatives. The most effective way to reduce the dissolution of electrodes in solvents is to improve intermolecular attraction between the electrode molecules by introducing π-π stacking and hydrogen bonds. Such all-around guidelines should promote the application of n-type PZ-based organic cathodes with a high redox potential and low electrode solubility for lithium batteries.

6.
Artigo em Inglês | MEDLINE | ID: mdl-31943699

RESUMO

Proton storage in rechargeable aqueous zinc-ion batteries (ZIBs) is attracting extensive attention owing to the fast kinetics of H+ insertion/extraction. However, it has not been achieved in organic materials-based ZIBs with a mild electrolyte. Now, aqueous ZIBs based on diquinoxalino [2,3-a:2',3'-c] phenazine (HATN) in a mild electrolyte are developed. Electrochemical and structural analysis confirm for the first time that such Zn-HATN batteries experience a H+ uptake/removal behavior with highly reversible structural evolution of HATN. The H+ uptake/removal endows the Zn-HATN batteries with enhanced electrochemical performance. Proton insertion chemistry will broaden the horizons of aqueous Zn-organic batteries and open up new opportunities to construct high-performance ZIBs.

7.
Angew Chem Int Ed Engl ; 59(8): 3048-3052, 2020 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-31721411

RESUMO

Understanding cation (H+ , Li+ , Na+ , Al3+ , etc.) intercalation/de-intercalation chemistry in transition metal compounds is crucial for the design of cathode materials in aqueous electrochemical cells. Here we report that orthorhombic vanadium oxides (V2 O5 ) supports highly reversible proton intercalation/de-intercalation reactions in aqueous media, enabling aluminum electrochemical cells with extended cycle life. Empirical analyses using vibrational and x-ray spectroscopy are complemented with theoretical analysis of the electrostatic potential to establish how and why protons intercalate in V2 O5 in aqueous media. We show further that cathode coatings composed of cation selective membranes provide a straightforward method for enhancing cathode reversibility by preventing anion cross-over in aqueous electrolytes. Our work sheds light on the design of cation transport requirements for high-energy reversible cathodes in aqueous electrochemical cells.

8.
Phys Chem Chem Phys ; 21(21): 11004-11010, 2019 Jun 07.
Artigo em Inglês | MEDLINE | ID: mdl-31089593

RESUMO

Benzoquinone (BQ)-based macrocyclic compounds have shown great potential as cathode materials for lithium-ion batteries (LIBs) owing to their high redox potential and specific capacity. However, such materials usually have complex structures, which impede the investigation of lithiation mechanisms. Herein, we take Calix[4]quinone (C4Q) molecule as an example to develop a viable mechanism investigation method for such materials. The lithiation profile of C4Q is determined by condensed Fukui function which provides the reaction sites and orders. A correction of redox potential is proposed by leaving out the ion-transfer effect during the redox reaction based on Gibbs free energy change. The redox potential obtained by this approach shows high consistency with the experimental results. Moreover, this method can also be well extended to study the lithiation mechanism of another BQ-based macrocyclic compound (Pillar[5]quinone). Our results are promising to more deeply understand the reaction mechanism and predict the redox potential of new BQ-based macrocyclic compounds for LIBs.

9.
Chem Sci ; 10(15): 4306-4312, 2019 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-31057757

RESUMO

All-solid-state sodium batteries have great potential for large-scale energy storage applications. However, constructing a compatible Na anode/solid-state electrolyte (SSE) interface is still challenging because most SSEs are unstable toward Na metal. A succinonitrile (SN) SSE shows high room-temperature ionic conductivity (10-3 S cm-1) but easily deteriorates if in contact with Na metal, leading to continuously increased interfacial resistance. Here we present an extremely simple approach to introduce a compact NaF-rich interphase on a Na surface via chemical reactions between fluoroethylene carbonate-Na+ and Na metal, resulting in a compatible Na anode/SN-based electrolyte interface. The in situ formed NaF-rich interphase can not only prevent side reactions between the SN-based electrolyte and Na anode but also regulate the uniform deposition of dendrite-free Na. As a result, the symmetric cells show a low overpotential of 150 mV after cycling for 4000 h. Furthermore, all-solid-state Na-CO2 batteries (4Na + 3CO2 ↔ 2Na2CO3 + C) with the compatible interface can run for 50 cycles with a small overpotential increase of 0.33 V. This work provides a promising method to build a stable interface that enables the use of an SSE which is unstable toward Na in Na metal batteries.

10.
Angew Chem Int Ed Engl ; 58(21): 7020-7024, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-30916877

RESUMO

Organic carbonyl compounds show potential as cathode materials for lithium-ion batteries (LIBs) but the limited capacities (<600 mA h g-1 ) and high solubility in electrolyte restrict their further applications. Herein we report the synthesis and application of cyclohexanehexone (C6 O6 ), which exhibits an ultrahigh capacity of 902 mA h g-1 with an average voltage of 1.7 V at 20 mA g-1 in LIBs (corresponding to a high energy density of 1533 Wh kg-1 C 6 O 6 ). A preliminary cycling test shows that C6 O6 displays a capacity retention of 82 % after 100 cycles at 50 mA g-1 because of the limited solubility in high-polarity ionic liquid electrolyte. Furthermore, the combination of DFT calculations and experimental techniques, such as Raman and IR spectroscopy, demonstrates the electrochemical active C=O groups during discharge and charge processes.

11.
Chem Sci ; 10(7): 2048-2052, 2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30842862

RESUMO

Nonaqueous potassium-ion hybrid capacitors (KIHCs) are faced with limited redox reaction kinetics of electrodes for accommodation of large-sized K+. Here, dipotassium terephthalate (K2TP) is applied as an organic negative electrode to provide comparable reaction kinetics with a non-faradaic activated carbon (AC) positive electrode to boost the electrochemical performance of KIHCs. It is revealed that the large exchange current density and fast two-dimensional (2D) diffusion pathways of K+ in K2TP determined by density functional theory (DFT) calculations ensure its fast redox reaction and transport kinetics. The as-constructed KIHC presents both high energy and power densities of 101 W h kg-1 and 2160 W kg-1 based on the mass of the two electrodes (41.5 W h kg-1 and 885.2 W kg-1 based on the mass of the two electrodes and electrolyte), respectively, and a superior capacity retention of 97.7% after 500 cycles. The excellent electrochemical performance is attributed to the fast kinetics, good structural flexibility, and small volume change (9.4%) of K2TP upon K+ insertion/extraction, and its good compatibility with the AC positive electrode in 1,2-dimethoxyethane (DME)-based electrolyte. This will promote application of organic materials in hybrid capacitors and the development of KIHCs.

12.
Angew Chem Int Ed Engl ; 57(30): 9443-9446, 2018 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-29863784

RESUMO

A key challenge faced by organic electrodes is how to promote the redox reactions of functional groups to achieve high specific capacity and rate performance. Here, we report a two-dimensional (2D) microporous covalent-organic framework (COF), poly(imide-benzoquinone), via in situ polymerization on graphene (PIBN-G) to function as a cathode material for lithium-ion batteries (LIBs). Such a structure favors charge transfer from graphene to PIBN and full access of both electrons and Li+ ions to the abundant redox-active carbonyl groups, which are essential for battery reactions. This enables large reversible specific capacities of 271.0 and 193.1 mAh g-1 at 0.1 and 10 C, respectively, and retention of more than 86 % after 300 cycles. The discharging/charging process successively involves 8 Li+ and 2 Li+ in the carbonyl groups of the respective imide and quinone groups. The structural merits of PIBN-G will trigger more investigations into the designable and versatile COFs for electrochemistry.

13.
J Phys Chem Lett ; 9(13): 3573-3579, 2018 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-29897763

RESUMO

This work is pioneering to introduce molecular electrostatic potential (MESP) to investigate the interaction between lithium ions and organic electrode molecules. The electrostatic potential on the van der Waals surface of the electrode molecule is calculated, and then the coordinates and relative values of the local minima of MESP can be correlated to the Li binding sites and sequence on an organic small molecule, respectively. This suggests a gradual lithiation process. Similar calculations are extended to polymers and even organic crystals. The operation process of MESP for these systems is explained in detail. Through providing accurate and visualizable lithium binding sites, MESP can give precise prediction of the lithiated structures and reaction mechanism of organic electrode materials. It will become a new theoretical tool for determining the feasibility of organic electrode materials for alkali metal ion batteries.

14.
Chem Commun (Camb) ; 54(50): 6792-6795, 2018 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-29756150

RESUMO

Here we report a flexible and rechargeable aqueous Zn-iodine battery with an iodine/carbon cloth cathode. Combined experimental and computational studies suggest that the battery undergoes a reversible reaction of Zn + I2 ↔ ZnI2 with suppressed I3- formation by confining iodine species in porous carbon.

15.
Phys Chem Chem Phys ; 20(19): 13478-13484, 2018 May 16.
Artigo em Inglês | MEDLINE | ID: mdl-29726879

RESUMO

Quinones are promising electrode materials for lithium-ion batteries (LIBs), but their structure-electrochemical property relationship remains unclear. The aim of this study is to unravel the structural influence on the electrochemical properties of different quinones in LIBs. Through density functional theory calculations, redox potentials of 20 parent quinone isomers were examined, which revealed an increasing order of redox potentials as para-quinones < discrete-quinones < ortho-quinones. Two new methods were introduced to calculate and design organic electrode materials rationally. One is the vertical electron affinity in consideration of solvation effect, which was used to estimate the number of electron accommodation for quinones during lithiation. The other is a new index denoted as ΔA2Li used in para- and ortho-quinones, which was introduced to reveal the relationship between aromaticity and redox potential, establishing the theoretical basis for the design of analogous high-voltage organic electrode materials of LIBs.

16.
Angew Chem Int Ed Engl ; 57(17): 4687-4691, 2018 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-29488300

RESUMO

Potassium-ion batteries (KIBs) are plagued by a lack of materials for reversible accommodation of the large-sized K+ ion. Herein we present, the Bi anode in combination with the dimethoxyethane-(DME) based electrolyte to deliver a remarkable capacity of ca. 400 mAh g-1 and long cycle stability with three distinct two-phase reactions of Bi↔ KBi2 ↔K3 Bi2 ↔K3 Bi. These are ascribed to the gradually developed three-dimensional (3D) porous networks of Bi, which realizes fast kinetics and tolerance of its volume change during potassiation and depotassiation. The porosity is linked to the unprecedented movement of the surface Bi atoms interacting with DME molecules, as suggested by DFT calculations. A full KIB of Bi//DME-based electrolyte//Prussian blue of K0.72 Fe[Fe(CN)6 ] is demonstrated to present large energy density of 108.1 Wh kg-1 with average discharge voltage of 2.8 V and capacity retention of 86.5 % after 350 cycles.

17.
Sci Adv ; 4(3): eaao1761, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-29511734

RESUMO

Quinones, which are ubiquitous in nature, can act as sustainable and green electrode materials but face dissolution in organic electrolytes, resulting in fast fading of capacity and short cycle life. We report that quinone electrodes, especially calix[4]quinone (C4Q) in rechargeable metal zinc batteries coupled with a cation-selective membrane using an aqueous electrolyte, exhibit a high capacity of 335 mA h g-1 with an energy efficiency of 93% at 20 mA g-1 and a long life of 1000 cycles with a capacity retention of 87% at 500 mA g-1. The pouch zinc batteries with a respective depth of discharge of 89% (C4Q) and 49% (zinc anode) can deliver an energy density of 220 Wh kg-1 by mass of both a C4Q cathode and a theoretical Zn anode. We also develop an electrostatic potential computing method to demonstrate that carbonyl groups are active centers of electrochemistry. Moreover, the structural evolution and dissolution behavior of active materials during discharge and charge processes are investigated by operando spectral techniques such as IR, Raman, and ultraviolet-visible spectroscopies. Our results show that batteries using quinone cathodes and metal anodes in aqueous electrolyte are reliable approaches for mass energy storage.

18.
Angew Chem Int Ed Engl ; 56(41): 12561-12565, 2017 10 02.
Artigo em Inglês | MEDLINE | ID: mdl-28787540

RESUMO

Application of organic electrode materials in rechargeable batteries has attracted great interest because such materials contain abundant carbon, hydrogen, and oxygen elements. However, organic electrodes are highly soluble in organic electrolytes. An organic electrode of 2,3,5,6-tetraphthalimido-1,4-benzoquinone (TPB) is reported in which rigid groups coordinate to a molecular benzoquinone skeleton. The material is insoluble in aprotic electrolyte, and demonstrates a high capacity retention of 91.4 % (204 mA h g-1 ) over 100 cycles at 0.2 C. The extended π-conjugation of the material contributes to enhancement of the electrochemical performance (155 mA h g-1 at 10 C). Moreover, density functional theory calculations suggest that favorable synergistic reactions between multiple carbonyl groups and lithium ions can enhance the initial lithium ion intercalation potential. The described approach may provide a novel entry to next-generation organic electrode materials with relevance to lithium-ion batteries.

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